Wireless optical mouse trouble

I'm starting this thread because I haven't seen anything that's quite the same as this problem. Using a basic Microsoft Wirless Optical mouse, IntelliPoint software (4.11). Over the last few weeks, it's started to jump, always a little down and to the left. If a document or web page is open, it causes it to scroll down just a bit when it does it. It's not opening or closing applications on its own, as others have done.

I've tried altering mouse pads, changing batteries, reseating the cables, etc. Driver version is 4.10.851.0. I can't find an updated driver for it, though there's an option to upgrade the software. Any other suggestions at all?